This invention relates generally to pop-up sprinklers for use in an irrigation system to water lawns, crops, and the like. More specifically, this invention relates to an improved pop-up sprinkler having a pressure-responsive control valve of simplified construction for sealing the sprinkler against water inflow to prevent leakage or drainage therethrough when water pressure is insufficient to move a pop-up stem rapidly to an elevated spraying position.
Pop-up sprinklers in general are well known in the art to include a spray nozzle carried at the upper end of a pop-up stem or riser which is in turn supported within a sprinkler housing for movement between retracted and elevated position in response to the pressure of water supplied to the sprinkler housing via a water supply line. More particularly, when water pressure is relatively low, such as when the water supply is turned off, the pop-up stem remains typically under the influence of a biasing spring in a position retracted substantially into the sprinkler housing with the spray nozzle disposed substantially flush with the upper end of the sprinkler housing. However, when water pressure is relatively high, such as when the water supply is turned on, the pressurized water acts against the underside of the pop-up stem to move the stem toward a position projecting upwardly from the sprinkler housing with the spray nozzle elevated above the sprinkler housing. In this elevated position, various seal structures cooperating between the stem and the housing confine the water flow to passage through the spray nozzle which is advantageously located above surrounding vegetation for unobstructed discharge of irrigation water.
One disadvantage encountered with pop-up sprinklers in general relates to leakage or drainage of water through the sprinkler when the pop-up stem is in any position other than the elevated spraying position. That is, substantial dimensional clearances are required between the pop-up stem and the sprinkler to accommodate stem movement between the retracted and elevated positions. These clearances, however, unfortunately define leakage paths through which water can flow in bypass relation with the sprinkler housing.
More specifically, during operation of a pop-up sprinkler, water leakage can occur during a relatively slow increase in water pressure, such as when the water supply is turned on slowly or when the water supply line is connected along its length to a relatively large number of sprinklers, whereby the pop-up stem moves relatively slowly from the retracted position to the elevated spraying position. Alternatively, when the water supply is turned off, water remaining in the supply line will drain through one or more pop-up sprinklers located at relatively low elevational positions in an irrigation system. In any event, water leakage or drainage can result in substantial quantities of wasted water which can be highly undesirable, particularly in relatively dry regions having limited water resources. Moreover, the wasted water tends to flood the area immediately surrounding the pop-up sprinkler to result in localized overwatering which can adversely affect plant development and growth.
In the past, various improvements to pop-up sprinklers have been proposed in an effort to reduce water waste from low pressure leakage or drainage through the sprinkler. For example, pop-up stem designs have been suggested wherein the stem has a relatively small cross-sectional area exposed to pressure when the water supply is turned on, thereby requiring a relatively high water pressure to initiate upward movement of the stem toward the elevated spraying position. Once this movement is initiated, a comparatively larger cross-sectional area of the stem is exposed to pressure resulting in a comparatively larger hydraulic force acting upon the stem to move the stem rapidly from the retracted position to the elevated position. While such stem designs advantageously minimize the time required for the stem to move from the retracted position to the elevated position, and thereby minimize leakage during such movement, they have not provided any satisfactory means for preventing water leakage or drainage when the water pressure in insufficient to displace the stem from the retracted position. Accordingly, substantial water leakage or drainage can still occur.
Some pop-up sprinkler stem designs have been proposed further to include a valve member or device for sealing the sprinkler against water inflow when the pop-up stem is in the retracted position. Such proposals, however, have resulted in relatively complex and expensive sprinkler constructions frequently having an undesirably large cross-sectional area of the pop-up stem exposed to water pressure. Accordingly, while leakage is prevented when the stem is in the retracted position, the stem pops up relatively slowly and at a relatively low pressure such that substantial leakage can still occur during movement to the elevated spraying position.
There exists, therefore, a significant need for an improved pop-up sprinkler having a pressure-responsive valve device of simplified, inexpensive construction and a relatively small cross-sectional size for sealing the sprinkler against water inflow until the water pressure reaches a predetermined level sufficient for rapid movement of the pop-up stem to an elevated spraying position. The present invention fulfills this need.